The cylinders of an internal combustion engine include intake and exhaust valves that are opened and closed by operation of one or more camshafts associated therewith. The camshaft typically includes one or more lobes that control the opening and closing profile of the associated intake/exhaust valve. The lobes are typically configured to accelerate the associate valve from its seat and maintain positive velocity until a peak lift of the valve from its seat is achieved.
Cylinder operations of internal combustion engine also involve controlling the timing of the opening and closing of the intake valves and the exhaust valves relative to one another to achieve desired combustion results. For example, opening the intake valve while the exhaust valve is opened during the exhaust stroke of the piston allows scavenging where intake air is drawn into the cylinder to facilitate forcing exhaust out of the cylinder. The ability to open the intake valve for cylinder scavenging is limited by clearance between the piston and valve as the piston approaches or is at top dead center. Therefore, further improvements in this area are needed.